1. Field of the Invention
The present invention relates to a system for loading and/or offloading objects that can be stacked and a loading and/or offloading station including this kind of system.
2. Description of the Prior Art
The present invention relates, for example, to loading and unloading supports for stacks of objects that can be stacked for use in a machine for printing the objects. The stack supports usually pass first through a loading station which moves a stack support from a conveyor belt or similar conveyor to a transfer station. At the transfer station the objects are unstacked to place them on the printing machine. The transfer system includes a robot, for example, with holding means for picking up a stacked object to put it down at a station of the printing machine.
An object of the present invention is to provide the simplest possible loading and/or unloading system between a system for feeding stacked object supports and a machine. The same system in accordance with the invention preferably loads and unloads stacked object supports.
To this end, the present invention proposes a system between a conveyor and a machine for loading and/or offloading a support for objects adapted to be stacked.
According to the invention, the system includes:
a carriage mobile in translation between a retracted position in which the carriage is moved away from the machine and an advanced position in which the carriage is close to the machine, the direction of movement of the carriage being substantially horizontal,
an arm adapted to push or pull a support, having at its free end a shape suitable for the support to be moved, and mounted on the carriage and articulated about a substantially vertical shaft, between a deployed position in which the free end of the arm is on the trajectory of a support and a retracted position folded toward the carriage, and
a spring return system spring-loading the arm toward its deployed position.
This provides a ratchet system of simple design that is easy to use. It suffices to orient the carriage substantially in the loading or offloading direction. In an initial position, the arm is positioned relative to a support to be moved and then, when the carriage moves, the support is entrained with the carriage toward its destination. At the end of the travel of the carriage, the support is no longer entrained and the carriage returns to its initial position. If during this return movement to the initial position the arm encounters a new support brought up by a conveyor, it folds toward the carriage and passes the obstacle without being impeded. Because of the return spring system, the arm returns automatically to its deployed position and is therefore in the correct position to entrain the new support with it the next time the carriage moves.
In some machines there is a difference in height between the plane in which the objects, in this instance the supports, are conveyed and the working plane of the machine. In such cases, the system according to the invention has the carriage cooperate with a platform intended to receive the support for objects to be stacked when the latter is loaded onto the machine or offloaded from it, either the carriage or the platform having an inclined plane with which the other cooperates. The platform then serves as an elevator. In this advantageous embodiment it is not necessary to provide a xe2x80x9cmotorxe2x80x9d for the elevator. The drive system of the loading and/or offloading device then moves the platform; either the carriage or the platform advantageously has an idler wheel adapted to cooperate with the inclined plane of the other one.
The loading and/or offloading system preferably includes a rotating transfer plate provided with housings each of which is adapted to receive a support adapted to be moved from the conveyor to the transfer plate or vice versa.
The present invention also proposes a loading and offloading system that includes two systems as described above, the carriages of the two systems being interconnected and moved by a common actuator. With this system a single actuator (piston and cylinder actuator, motor or the like) handles loading and offloading, which is highly advantageous. It saves space and reduces costs compared to prior art systems.
In one advantageous embodiment each carriage is mounted to slide on a guide rail and the two guide rails are fastened together by a base. The base is substantially triangular, for example. The carriages can then be placed on respective opposite sides of the base and their guide rails form two sides of the triangle. Each carriage is then advantageously connected by a link of variable length to a mobile central block moved by an actuator.
The mobile central block advantageously includes at the front, i.e. on the same side as the machine, an idler wheel adapted to cooperate with an inclined plane disposed under a platform intended to receive the support for objects to be stacked when the latter is loaded onto the machine or offloaded from it. There is then no need to provide a toothed wheel on each carriage.
The present invention also relates to a station for loading and offloading supports for objects intended to be stacked, the station including a conveyor, a rotating transfer plate provided with housings each adapted to receive a support, and a system for moving a support from the conveyor toward the transfer plate or vice versa.
In accordance with the invention, the system for moving a support includes a loading and/or offloading system as described above or a loading and offloading system as described above.
In the case of a loading and offloading station including a system for loading and offloading simultaneously and in which the supports to be moved each have a base having a circular cylindrical foot on which is placed a circular plate of greater diameter than the foot, the housings of the transfer plate adapted to receive a support advantageously open onto the periphery of the plate, thus providing a lateral opening for each housing, the resulting openings enabling radial introduction of a support foot but preventing radial introduction of a circular support plate. This kind of plate facilitates introducing supports onto the plate. The prior art plates have housings that do not open onto the periphery, which necessitate a relatively large vertical travel of the support to accommodate it on the plate, but the embodiment proposed here significantly limits the vertical movement necessary to place the support in its housing.
In this advantageous embodiment, each housing has a peripheral shoulder, defining two bores with different diameters; the larger diameter bore is adapted to receive a support plate with as little clearance as possible and the smaller diameter bore is adapted to receive a support foot. The support is therefore perfectly retained in its housing.
As already mentioned above, the loading and offloading station can include a platform under the transfer plate, facing the loading and offloading system, and having a substantially horizontal upper face adapted to receive a support and mobile in translation in a substantially vertical direction between a top position, in which the upper face of the platform is substantially in the plane in which the supports are conveyed, and a bottom position, in which the upper face is below a support foot, without touching the latter when the support is placed in its housing on the rotating plate.
The present invention also proposes a printing machine including a circular contour printing table which has a plurality of object-stations regularly distributed around its periphery each adapted to receive an object to be printed, a loading station and an offloading station, wherein at least one loading and/or offloading station includes a loading and/or offloading system as described above or a loading and offloading system as described above.
In the latter case, the printing machine advantageously includes two transfer plates, each transfer plate is advantageously associated with a loading and offloading system as described above, a conveyor is preferably provided for feeding supports to a first loading and offloading system, a system is advantageously provided for conveying empty supports offloaded from the first transfer plate by the first loading and offloading system to the second loading and offloading system in order to be loaded onto the second transfer plate, and a second conveyor is provided, for example, to transport away the filled supports offloaded from the second transfer plate by the second loading and offloading system.
The following description with reference to the accompanying diagrammatic drawings explains further the objects and advantages of the invention. It is clear that the description is given by way of example only and is not limiting on the invention.